Load indicating fasteners

Abstract

A load indicating fastener composed of a body (2) having an abutment (9) which is moved by the changing length of the body (2) under an applied load, and a load sensing member (10) composed of an element (11) disposed in the direction in which a load is applied to the body (2) when the fastener is in the user characterized in that the element (11) is of elongated U-shape, a first limb (13) of the U providing an anchorage part (14) which is rigidly anchored to the body (2), the closed end of the U providing a bearing part (15) which bears on the abutment (9) so as to move with the abutment relative to the anchorage part (14) in response to a load applied to the body, and a second limb (16) of the U having an indicator (17) at its outer end which responds movement of the bearing part (15) and registers the applied load related to that movement on a scale (19).

We claim: 
     
       1. A load indicating fastener comprising a body (2) having an abutment (9) which is moved by the changing length of the body (2) under an applied load, and load sensing means (10) comprising an element (11) disposed in the direction in which a load is applied to the body (2) when the fastener is in use characterised in that the element (11) is of elongated U-shape, a first limb (13) of the U providing an anchorage part (14) which is rigidly anchored to the body (2), the closed end of the U providing a bearing part (15) which bears on the abutment (9) so as to move with the abutment relative to the anchorage part (14) in response to a load applied to the body, and a second limb (16) of the U having an indicator (17) at its outer end which responds to movement of the bearing part (15) and registers the applied load related to that movement on a scale (19). 
     
     
       2. A load indicating fastener according to claim 1 characterised in that the element (11) is made of a material having the same coefficient of thermal expansion as the material of the body (2). 
     
     
       3. A load indicating fastener according to claim 2 characterised in that the element (11) is made of wire. 
     
     
       4. A load indicating fastener according to claim 2 characterised in that the limbs (13,16) of the element (11) are resiliently movable relative to one another about the bearing part (15) in response to movement of the bearing part with the abutment (9). 
     
     
       5. A load indicating fastener according to claim 2 characterised in that at least in part the load sensing means (10) is located in a blind bore or passage (7) in the body (2). 
     
     
       6. A load indicating fastener according to claim 5 characterised in that the abutment (9) is formed by the closed end of the bore or passage (7). 
     
     
       7. A load indicating fastener according to claim 5 characterised in that the abutment (9) is provided by an insert (27) in the closed end portion of the bore or passage (7). 
     
     
       8. A load indicating fastener according to claim 2 characterised in that the anchorage part (14) of the element is anchored to a support (12) fixed to the body (2) and closing the bore or passage (7). 
     
     
       9. A load indicating fastener according to claim 8 characterised in that the scale (19) is on the support (12). 
     
     
       10. A load indicating fastener according to claim 8 or claim 9 characterised in that the second limb (16) of the element (11) passes through an opening (18) in the support (12) to the scale (19). 
     
     
       11. A load indicating fastener according to claim 5 characterised in that the anchorage part (28) of the element (11) is anchored directly to the body (2). 
     
     
       12. A load indicating fastener according to claim 11 characterised in that the anchorage part (29) is in the form of a coil which is anchored in a mouth (8) of the bore or passage (7). 
     
     
       13. A load indicating fastener according to claim 2 characterised in that the load sensing means (10) is adapted to give a signal that a given load or loads has or have been applied to the body (2) when the fastener is in use. 
     
     
       14. A load indicating fastener according to claim 13 characterised in that the load sensing means (10) is contained in an electrical circuit designed to produce an audible and/or visual signal when a given load or loads is or are registered on the scale (19). 
     
     
       15. A load indicating fastener according to claim 13 characterised in that the load sensing means (10) is contained in an electrical circuit adapted to operate means for applying load on the body (2) in use of the fastener. 
     
     
       16. A load indicating fastener according to claim 1 characterised in that the element (11) is made of wire. 
     
     
       17. A load indicating fastener according to claim 1 characterised in that the limbs (13, 16) of the element (11) are resiliently movable relative to one another about the bearing part (15) in response to movement of the bearing part with the abutment (9). 
     
     
       18. A load indicating fastener according to claim 1 characterised in that at least in part the load sensing means (10) is located in a blind bore or passage (7) in the body (2). 
     
     
       19. A load indicating fastener according to claim 1 characterised in that the anchorage part (14) of the element is anchored to a support (12) fixed to the body (2) and closing the bore or passage (7). 
     
     
       20. A load indicating fastener according to claim 1 characterised in that the load sensing means (10) is adapted to give a signal that a given load or loads has or have been applied to the body (2) when the fastener is in use.